1. Field of the Invention
The present invention relates to a solid-state imaging device, a signal processing method of a solid-state imaging device, and an electronic apparatus.
2. Description of the Related Art
In a solid-state imaging device, such as a CCD (Charge Coupled Device) image sensor and a CMOS (Complementary Metal-Oxide Semiconductor) image sensor, unit pixels are in many cases arranged in a grid-like pattern at a predetermined pitch in the vertical and horizontal directions (see Japanese Unexamined Patent Application Publication No. 2007-189085, for example).
A pixel array having the same pitch in the vertical and horizontal directions is easily signal-processed, and thus has become a mainstream these days. Pixels arranged at the same pitch in the vertical and horizontal directions, i.e., pixels each having the same size in the vertical and horizontal directions are called square pixels. Meanwhile, pixels arranged at different pitches in the vertical and horizontal directions, i.e., pixels each having different sizes in the vertical and horizontal directions are called rectangular pixels.
In a solid-state imaging device used in an old type video camera or the like, rectangular pixels longer in the vertical size than in the horizontal size are used in many cases. This is because, in television broadcasting standards, the number of scanning lines running in the vertical direction is specified, but there is a degree of freedom in the number of scanning lines running in the horizontal direction, and therefore the advantage of using square grid pixels is minor if the intended purpose is to display an image on a television.
Meanwhile, for the purposes of performing image processing by using a personal computer and performing real-time extraction and recognition of a characteristic of an image by using machine vision, the square pixels are preferable to the rectangular pixels. In view of this, this type of solid-state imaging device, i.e., a solid-state imaging device using the square pixels has been increasingly used in video cameras.
Further, to provide a solid-state imaging device with a new function or an improved characteristic, a method of performing calculation between pixels mutually adjacent in the vertical or horizontal direction (hereinafter described as “adjacent pixels”) is employed in some cases. For example, there has been a method of using different accumulation times for the pixels of even rows and the pixels of odd rows as a method of increasing the dynamic range (see Japanese Unexamined Patent Application Publication No. 11-150687, for example).
According to this method of increasing the dynamic range, however, if the dynamic range is increased on the basis of one image, the resolution in the vertical direction is reduced by half. In Japanese Unexamined Patent Application Publication No. 11-150687, two images are used to compensate for the resolution in the vertical direction. Instead, however, the dynamic resolution is deteriorated due to time lag. If calculation is thus performed between adjacent pixels in the vertical or horizontal direction, the resolution in the direction is changed. Consequently, a resultant output becomes equal to the output from the rectangular pixels.